Quadratkilometer

Square kilometre (U.S. spelling: square kilometer), symbol km², is a decimal multiple of the SI unit of surface area, the square metre, one of the SI derived units. 1 km² is equal to: 1,000,000 m²100 ha (hectare)Conversely:1 m² = 0.000 001 (10-6) km²1 hectare = 0.01 (10-2) km²1 square mile = 2.589 988 km²1 acre = 0.004 047 km², 40.47 ha or 4047 m²Note: "km²" means (km)², square kilometre or kilometre squared, and not k(m²), kilo–square metre. For example, 3 km² is equal to 3 * (1,000 m)² = 3,000,000 m², not 3,000 m².
See more at Wikipedia.org...

n. square kilometer, area whose length and width are both one kilometer, area of one thousand dunams